This invention relates to a gas-fired heating apparatus, in particular a heating apparatus of the type having radiant bodies to be heated by gas flames, and in which fuel gas and combustion air are supplied under pressure to at least one burner nozzle in a proportion ensuring complete combustion, and further comprising an air chamber in association with said at least one burner, said chamber having an outlet terminating in the ambient space, a venturi extending from said chamber into the burner, and a gas supply nozzle disposed within the chamber coaxially in front of the venturi throat, as disclosed in JP-A-59 202318 (MATSUSHITA DENKI SANGYO K.K.).
An advantage of such an apparatus is that no polluted air is sucked in from the ambient space, which may give rise to fouling of burners.
In the prior apparatus, the air supply and gas supply are controlled in dependence upon measurements of the air pressure within the air chamber and the gas pressure within the gas supply conduit to the nozzle. When the type of gas is changed adjustment is effected with throttle means in the gas supply path and in the outlet to the outside air, the arrangement being such that the adjusted ratio has a constant value.
With the advent of new gas radiators, however, which can be operated through a large range of their capacity (e.g. from 3-100%) by controlling the gas supply pressure, the problem has been introduced that complex measures are required to maintain the correct gas/air ratio throughout the entire control range.